Apparatus and method for performing ligand binding assays on microarrays in multiwell plates

Each well of a multiwell plate adapted to accept a plurality of biological samples for testing for the presence of analytes in the sample is further adapted herein for immobilizing on the side walls of a well a 3D arrangement of ligand arrays. A well is formed with planar side walls and a stack of sample separators is placed within a well in positions so as to not come in contact with ligand spots in the array(s). The spacing between each pair of adjacent separators in a stack forms a sample chamber in a position corresponding to an array of the 3D arrangement of ligand arrays.